Imports System
Imports System.Collections.Generic
Class NonRepeatedCharacter
Public Shared Sub Main()
Dim str As String = "ppdadxefe"
Dim result As Char? = FindFirstNonRepeatedChar(str)
Console.WriteLine(If(result.HasValue, $"First non-repeated character: {result}", "No non-repeated character found."))
End Sub
Private Shared Function FindFirstNonRepeatedChar(ByVal str As String) As Char?
Dim charCount = New Dictionary(Of Char, Integer)()
For Each ch As Char In str
If charCount.ContainsKey(ch) Then
charCount(ch) += 1
Else
charCount(ch) = 1
End If
Next
For Each ch As Char In str
If charCount(ch) = 1 Then Return ch
Next
Return Nothing
End Function
End Class
' run:
'
' First non-repeated character: a
'
